Abhishek Jauhari | University of Pittsburgh (original) (raw)

Papers by Abhishek Jauhari

Journal of Clinical Investigation

Chronic inflammation is a pathologic feature of neurodegeneration and aging; however, the mechani... more Chronic inflammation is a pathologic feature of neurodegeneration and aging; however, the mechanism regulating this process is not understood. Melatonin, an endogenous free radical scavenger synthesized by neuronal mitochondria, decreases with aging and neurodegeneration. We proposed that insufficient melatonin levels impair mitochondrial homeostasis resulting in mitochondrial DNA (mtDNA) release, activation of cytosolic DNA mediated inflammatory response in neurons. We found increased mitochondrial oxidative stress and decreased mitochondrial membrane potential with higher mitochondrial DNA (mtDNA) release in brain and primary cerebro-cortical neurons of melatonin deficient aralkylamine N-acetyltransferase (AANAT) knockout mice. Cytosolic mtDNA activated the cGAS/STING/IRF3 pathway, stimulating inflammatory cytokine generation. We found that Huntington's disease mice increased mtDNA release, cGAS activation, and inflammation, all inhibited by exogenous melatonin. Thus, we demonstrated that cytosolic mtDNA activated the inflammatory response in aging and neurodegeneration, a process modulated by melatonin. Furthermore, our data suggest that AANAT knockout mice are a model of accelerated aging.

MicroRNAs (miRNAs) have emerged as a new class of RNA molecules which are short in length, less i... more MicroRNAs (miRNAs) have emerged as a new class of RNA molecules which are short in length, less in number but play bigger role in regulation of cellular events. miRNAs keep cellular homeostasis in tight control by fine tuning expression of protein coding genes at post-transcriptional level. Neurogenesis and neurodegeneration are two complex processes which are regulated by dynamic expression of regulatory proteins like transcription factors and signaling proteins. Evidences are accumulating that expression of miRNAs play major role in fate determination of neuronal cells undergoing neurogenesis or neurodegeneration. Neurodegeneration either induced by genetic factors or environmental chemicals results in development of neurodegenerative disorders like Parkinson's or Alzheimer's. With increasing acceptance of adult neurogenesis, it seems possible that inducing neurogenesis in adult brain can help in fighting with neurodegenerative disorders. Regulatory RNA molecules, like miRNAs are presenting them as potential therapeutic targets for inducing neurogenesis and controlling neurodegeneration. In the current review, we are exploring the link between neurodegeneration and adult neurogenesis regulation by focusing on miRNAs.

The generation of differentiated and functional neurons is a complex process, which requires coor... more The generation of differentiated and functional neurons is a complex process, which requires coordinated expression of several proteins and microRNAs (miRNAs). The present study using nerve growth factor (NGF)-differentiated PC12 cells led to the identification of miR-200, miR-221/222 and miR-34 families as major up-regulated miRNAs in fully differentiated neurons. Similar to PC12 cells, induction of miR-200 family was observed in differentiating neural stem cells, demonstrating a direct role of miR-200 family in neuronal differentiation. Over-expression of miR-200 induced neurite formation in PC12 cells and regulated neuronal markers in favour of differentiation. However, inhibition of miR-200 induced proliferation of PC12 cells. In differentiating PC12 cells and neural stem cells, an inverse relationship was observed between expression of reprogramming transcription factors (SOX2, KLF4, NANOG, OCT4 and PAX6) and miR-200. Over-expression of miR-200 in PC12 cells significantly down-regulated mRNA and protein levels of SOX2 and KLF4. Moreover, we observed two phases of dramatic down-regulation of miR-200 expression in developing rat brains correlating with periods of neuronal proliferation. In conclusion, our results indicate that increased expression of the miR-200 family promotes neuronal differentiation , while decreased expression of the miR-200 family promotes neuronal proliferation by targeting SOX2 and KLF4.

Abstract Alzheimer's disease (AD) is a devastating neurodegenerative disorder, characterized by ... more Abstract Alzheimer's disease (AD) is a devastating neurodegenerative disorder,
characterized by extensive loss of neurons and deposition of amyloid β (Aβ) in the form of
extracellular plaques. Aβ is considered to have a critical role in synaptic loss and neuronal
death underlying cognitive decline. Platelets contribute to 95% of circulating amyloid
precursor protein that releases Aβ into circulation. We have recently demonstrated that the
Aβ active fragment containing amino acid sequence 25–35 (Aβ 25–35) is highly
thrombogenic in nature and elicits strong aggregation of washed human platelets in a RhoA-
dependent manner. In this study, we evaluated the influence of fibrinogen on Aβ-induced
platelet activation. Intriguingly, Aβ failed to induce aggregation of platelets suspended in
plasma but not in buffer. Fibrinogen brought about dose-dependent decline in …

Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinate... more Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinated expression of mRNA, microRNAs (miRNAs) and regulatory proteins. Our earlier unbiased miRNA profiling studies have identified miR-200, miR-34 and miR-221/222 as maximally up-regulated miRNA families in differentiating PC12 cells and demonstrated the capability of miR-200 family in inducing neuronal differentiation (J. Neurochem, 2015, 133, 640– 652). In present study, we have investigated role of miR-34 family in neuronal differentiation and identified P53 as mediator of nerve growth factor (NGF) induced miR-34a expression in differentiating PC12 cells. Our studies have shown that NGF induced miR-34a, arrests proliferating PC12 cells to G1 phase, which is prerequisite for neuronal differentiation. Our studies have also shown that increased expression of miR-34a controls the P53 level in differentiated PC12 cells in feedback inhibition manner, which probably prevents differentiated cells from P53 induced apoptosis. Expression profiling of miR-34 family in different neuronal, non-neuronal and developing cells have identified differentiated and aged brain cells as richest source of miR-34, which also indicates that higher expression of miR-34 family helps in maintaining the mature neurons in non-proliferative stage. In conclusion, our studies have shown that miR-34 is brain enriched miRNA family, which up-regulates with neuronal maturation and brain ageing and cooperative regulation of P53 and miR-34a helps in neu-ronal differentiation by arresting cells in G1 phase.

MicroRNAs (miRNAs) are generated by endonucle-ase activity of Dicer, which also helps in loading of

Cypermethrin, a pyrethroid pesticide, has been shown to induce neurotoxicity in adult mammals. Ho... more Cypermethrin, a pyrethroid pesticide, has been shown to induce neurotoxicity in adult mammals. However, studies are also needed to explore its toxicity in developing brains and understand its mechanism of action in neurons. In our recently published study, using nerve growth factor (NGF) differentiated PC12 cells, we have identified the miR-200 family as major up-regulated miRNAs, which regulate differentiation of PC12 cells into neurons. In the present study, the toxicity of cypermethrin is compared between undifferentiated and neuron-like differentiated PC12 cells, and role of the miR-200 family is studied in cypermethrin-induced neuronal cell death. Our studies have shown that a non-cytotoxic concentration of cypermethrin selectively induces the miR-200 family and apoptosis in differentiated PC12 cells, while no significant alterations were observed in undifferentiated PC12 cells. Further, our studies have demonstrated that cypermethrin induces miR-200 by increasing P53 levels in differentiated PC12 cells and we have identified a direct correlation between the expression of miR-200 and levels of P53 in PC12 cells. Further, BCL2 is identified as a target protein of miR-200b/c, and down-regulation of the BCL2 protein regulates cypermethrin-induced apoptosis of differentiated PC12 cells. Rescue experiments carried out with inhibitors of the miR-200 family, have further confirmed the role of the miR-200 family in apoptosis of differentiated PC12 cells exposed to cypermethrin. In conclusion, our studies have shown that differentiated PC12 cells are more sensitive to cypermethrin exposure than naïve and undifferentiated PC12 cells, and P53 mediated induction of the miR-200 family regulates cypermethrin-induced apoptosis of differentiated neuron-like PC12 cells.

Cypermethrin, a pyrethroid pesticide, has been shown to induce neurotoxicity in adult mammals.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder, characterized by extensive ... more Alzheimer's disease (AD) is a devastating neurodegenerative disorder, characterized by extensive loss of neurons and deposition of amyloid β (Aβ) in the form of extracellular plaques. Aβ is considered to have a critical role in synaptic loss and neuronal death underlying cognitive decline. Platelets contribute to 95% of circulating amyloid precursor protein that releases Aβ into circulation. We have recently demonstrated that the Aβ active fragment containing amino acid sequence 25-35 (Aβ 25-35 ) is highly thrombogenic in nature and elicits strong aggregation of washed human platelets in a RhoA-dependent manner. In this study, we evaluated the influence of fibrinogen on Aβ-induced platelet activation. Intriguingly, Aβ failed to induce aggregation of platelets suspended in plasma but not in buffer. Fibrinogen brought about dose-dependent decline in aggregatory response of washed human platelets elicited by Aβ 25-35 , which could be reversed by increasing doses of Aβ. Fibrinogen also attenuated Aβ-induced platelet responses such as secretion, clot retraction, rise in cytosolic Ca +2 and reactive oxygen species. Fibrinogen prevented intracellular accumulation of full-length Aβ peptide (Aβ 42 ) in platelets as well as neuronal cells. We conclude that fibrinogen serves as a physiological check against the adverse effects of Aβ by preventing its interaction with cells. online address: http://www.molmed.org

Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinate... more Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinated expression of mRNA, microRNAs (miRNAs) and regulatory proteins. Our earlier unbiased miRNA profiling studies have identified miR-200, miR-34 and miR-221/222 as maximally upregulated miRNA families in differentiating PC12 cells and demonstrated the capability of miR-200 family in inducing neuronal differentiation (J. Neurochem, 2015, 133, 640-652). In present study, we have investigated role of miR-34 family in neuronal differentiation and identified P53 as mediator of nerve growth factor (NGF) induced miR-34a expression in differentiating PC12 cells. Our studies have shown that NGF induced miR-34a, arrests proliferating PC12 cells to G1 phase, which is pre-requisite for neuronal differentiation. Our studies have also shown that increased expression of miR-34a controls the P53 level in differentiated PC12 cells in feedback inhibition manner, which probably prevents differentiated cells from P53 induced apoptosis. Expression profiling of miR-34 family in different neuronal, non-neuronal and developing cells have identified differentiated and aged brain cells as richest source of miR-34, which also indicates that higher expression of miR-34 family helps in maintaining the mature neurons in non-proliferative stage. In conclusion, our studies have shown that miR-34 is brain enriched miRNA family, which up-regulates with neuronal maturation and brain ageing and co-operative regulation of P53 and miR-34a helps in neuronal differentiation by arresting cells in G1 phase.

are generated by endonuclease activity of Dicer, which also helps in loading of miRNAs to their t... more are generated by endonuclease activity of Dicer, which also helps in loading of miRNAs to their target sequences. SH-SY5Y, a human neuroblastoma and a cellular model of neurodevelopment, consistently expresses genes related to neurodegenerative disorders at different biological levels (DNA, RNA, and proteins). Using SH-SY5Y cells, we have studied the role of Dicer and miRNAs in neuronal differentiation and explored involvement of P53, a master regulator of gene expression in differentiation-induced induction of miRNAs. Knocking down Dicer gene induced senescence in differentiating SH-SY5Y cells, which indicate the essential role of Dicer in brain development. Differentiation of SH-SY5Y cells by retinoic acid (RA) or RA + brain-derived neurotrophic factor (BDNF) induced dramatic changes in global miRNA expression. Fully differentiated SH-SY5Y cells (5-day RA followed by 3-day BDNF) significantly (p < 0.05 and atleast >3-fold change) upregulated and downregulated the expression of 77 and 17 miRNAs, respectively. Maximum increase was observed in the expression of , and miR-222 after RA + BDNF exposure in SH-SY5Y cells. Exploring the role of P53 in differentiating SH-SY5Y cells, we have observed that induction of miR-222, miR-192, and miR-145 is P53 dependent and expression of miR-193a-5p, miR-199a-5p, miR-146a, miR-21, miR-153, and miR-29b is P53 independent. In conclusion, decreased Dicer level enforces differentiating cells to senescence, and differentiating SH-SY5Y cells needs increased expression of P53 to cope up with changes in protein levels of mature neurons.

Journal of Clinical Investigation

MicroRNAs (miRNAs) are generated by endonucle-ase activity of Dicer, which also helps in loading of

Cypermethrin, a pyrethroid pesticide, has been shown to induce neurotoxicity in adult mammals.

Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinate... more Differentiation of neural stem cells (NSC's) to mature and functional neurons requires coordinated expression of mRNA, microRNAs (miRNAs) and regulatory proteins. Our earlier unbiased miRNA profiling studies have identified miR-200, miR-34 and miR-221/222 as maximally upregulated miRNA families in differentiating PC12 cells and demonstrated the capability of miR-200 family in inducing neuronal differentiation (J. Neurochem, 2015, 133, 640-652). In present study, we have investigated role of miR-34 family in neuronal differentiation and identified P53 as mediator of nerve growth factor (NGF) induced miR-34a expression in differentiating PC12 cells. Our studies have shown that NGF induced miR-34a, arrests proliferating PC12 cells to G1 phase, which is pre-requisite for neuronal differentiation. Our studies have also shown that increased expression of miR-34a controls the P53 level in differentiated PC12 cells in feedback inhibition manner, which probably prevents differentiated cells from P53 induced apoptosis. Expression profiling of miR-34 family in different neuronal, non-neuronal and developing cells have identified differentiated and aged brain cells as richest source of miR-34, which also indicates that higher expression of miR-34 family helps in maintaining the mature neurons in non-proliferative stage. In conclusion, our studies have shown that miR-34 is brain enriched miRNA family, which up-regulates with neuronal maturation and brain ageing and co-operative regulation of P53 and miR-34a helps in neuronal differentiation by arresting cells in G1 phase.